Galileo's Opere

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Galileo Galilei (1564-1642) was born in Pisa where he entered the University at the age of 17, originally as a medical student. Later he turned to mathematics and continued his education at Padua which was, in effect, the university for the major maritime power of Venice. In 1609 he constructed an improved version of a new Dutch invention – the telescope.

Although some historians disagree as to who first turned a telescope to the heavens it can still be claimed that Galileo was the first person to use the refracting telescope to make important astronomical observations. These observations convinced him of the accuracy of Copernicus’ heliocentric theory of the motion of the planets (that the planets revolve around the sun) rather than the Roman Catholic Church’s approved theory that the planets revolved around the Earth. By this time he was a professor of astronomy at the University of Pisa and, as such required to teach the Church’s approved doctrine. His defence against thinking for himself rather than thinking what the Church told him to think was the reasonable ‘I do not feel obliged to believe that the same God who has endowed us with sense, reason and intellect has intended us to forgo their use’. His refusal to teach what he was told led in 1633 to the Penitentiary College (otherwise known as the Inquisition) convicting him of the crime of heresy, forcing him to withdraw publicly his support of Copernicus and sentencing him to life imprisonment. Because of his old age this was moderated to house arrest. Therefore he spent the last nine years of his life at his villa in Florence.

Galileo's originality as a scientist was in his methodology, his propensity for reducing problems to their basics, applying common sense and logic and then analysing and resolving them according to simple mathematical descriptions. His ‘Law of Inertia’ was the foundation of Isaac Newton’s ‘First Law of Motion’.

Historical Collection 1 contains the following from the works of Galileo:

The four volumes on Galileo’s philosophy and mathematics are written in the form of dialogues and letters and the first volume includes a life of Galileo.

You can learn more about Galileo on this website:

Galileo the Heaven Gazer, part of our 'Virtual observatory' gallery discusses his work with the telescope in greater detail and also discusses the great man's own eyesight, a topic which remains the subject of much speculation but little verifiable fact.

Galileo Galilei, part of our 'Virtual art gallery' section discusses an English-made portrait of Galileo hanging in the College of Optometrists.